1. Field of the Invention
The present invention relates generally to wall fasteners and in particular to fasteners used to secure objects to both solid core walls and hollow walls made of lightweight material, such as gypsum board or the like.
2. Description of the Background Art
Wall fasteners are typically installed in solid core walls or in hollow walls made of lightweight material, such as gypsum board, to attach objects to the wall. Such fasteners are useful in supporting relative heavy objects, such as framed pictures or shelves that are attached to the wall. According to prior practice, for example, fasteners installed in hollow walls are comprised of a threaded member, such as a bolt or screw, and an anchoring mechanism. Rotation of the threaded member causes the anchoring mechanism to expand and contact the inside of the wall to anchor the fastener in place. Common examples of such fasteners are the so-called "toggle" bolts and "moly" bolts. Various types of fasteners are described in the following U.S. Pat. Nos.: 4,136,599; 4,086,840; 4,077,300; 3,905,570; 3,874,264; 3,869,958; 3,752,032; 3,701,302; 3,605,846; 3,555,960; 3,534,797; 3,487,746; 3,366,405; 3,315,558; 3,211,044; 3,136,350; 3,104,582; and 1,978,935.
One problem associated prior art fasteners of the above type is that a portion of the anchoring mechanism is usually received within the hole in the wall through which the fastener is inserted. Therefore, stress exerted by heavy objects attached to the fastener on the outside of the wall may cause the fastener to pull outwardly through the opening. Another problem is that the fasteners must be carefully installed to insure that they are not over-torqued. Continued twisting of the threaded bolt or screw after the anchoring mechanism has contacted the inner surface of the wall will cause the anchoring mechanism to twist and dig into the inner surface of the wall. This digging action gouges the periphery of the wall hole, which causes the fastener to fit loosely within the wall and thereby increases the likelihood that the fastener will become dislodged from the wall.
Additionally, the supporting capacity/strength of conventional fastening structures is limited by a relatively short axis of rotation in the axial plane. As will be readily appreciated by those skilled in the art, this axis is defined by the distance between the points of support provided by the anchoring assembly and threaded member. In the case of prior art configurations such, for example, as the "moly" bolt, this distance is equivalent to the thickness of the wall or wallboard and is typically far too short to support large or heavy objects due to the high concentration of stresses over such a small area.